Induction motors and universal motors are being used in most applications requiring constant-speed and low-horsepower, mainly because of their competitive cost. To replace such conventional motors, research has been conducted on single-phase switched reluctance motor (“SRM”) drives over the last decade. However, single-phase SRM drives are not suitable for high performance applications since they have some inherent limitations, including low output power density and only a 50% duty cycle of torque generation. They also require an additional component in the form of permanent magnets or auxiliary windings for self-starting.
Because of the known deficiencies of single-phase SRMs, more attention has been paid to two-phase SRM drives, especially for high torque and/or high-efficiency applications. For instance, two-phase SRM drives are positioned as brushless motor drives in variable-speed applications, such as those found in home appliances and power tools. One drawback of conventional two-phase SRM drives is their cost. Two-phase SRM drives typically may require equal, more, or less steel and magnet wire than single-phase SRMs and multiphase (greater than 2 phases) SRMs. Thus, one of the ways that two-phase SRM drives can distinguish themselves in the marketplace is by reducing their cost in comparison to conventionally available SRMs and hence to all other machines that are in practice.
Accordingly, it is generally desirable to provide a low-cost, two-phase SRM drive that can be deployed in high torque and/or high-efficiency applications. The two-phase SRM drive should cost less than currently available two-phase SRM drives without having to sacrifice torque output or motor efficiency.